The present invention relates to a device and method for generating information in which a plurality of files are enumerated. Particularly, the present invention relates to a device and method for generating information in which a plurality of files on a sequential medium are enumerated.
In the case of copying a plurality of files or scanning a plurality of files for computer viruses, the plurality of files is sequentially read from a storage. In this process, if the storage is a random-accessible medium such as a hard disk drive (HDD) or a universal serial bus (USB) memory, the order of accessing the files does not make any difference.
If the storage is a sequentially-accessed medium, such as a tape, however, it may require a long period of time for reading the plurality of files depending on the order of accessing the files in some cases.
Actually, even in the case of using a linear tape file system (LTFS), which is a standard file system on a tape conforming to the Linear Tape-Open (LTO) standard, the performance (a required period of time) largely depends on the order of copying the files if the locations where the files are recorded are not sequential on the tape when the files on the LTFS are copied into the HDD.
For example, it is assumed that a file A, a file B, and a file C are written in this order in a tape. In this case, if the file A, the file B, and the file C are accessed in this order, the files are able to be read at a speed of maximum 140 MB/s in the LTO fifth generation. If the file C, the file B, and the file A are accessed in this order, however, the files may be able to be read at a speed of only several MB/s or so in some cases.
As described above, the order of accessing files is largely related to the performance in the case of copying the files in the LTFS into the HDD.
There is known a technique described in an official gazette for improving the efficiency of accessing files by considering the order of the accessed files (for example, refer to Japanese Patent Application Publication No. JP2010-97646A).
In Japanese Patent Application Publication No. JP2010-97646A, a tape drive controller includes a tape running control unit which controls the running of a tape, a read/write control unit which controls a head, and a seek management table in which seek times from the beginning of tape (BOT) are registered in the order of written files. In the seek management table, seek time is provisionally registered with respect to a file whose seek time is unconfirmed. If the seek information is confirmed afterward, the confirmed seek time is registered. When a request is made to read a plurality of files, the tape running control unit controls the running of the tape to enable the head to access the plurality of files requested to be read in ascending order of the seek time by referring to the seek management table.
In addition to the above, there have been suggested other various techniques described in official gazettes for speeding up the access to files (for example, refer to Japanese Patent Application Publication No. JP02-246075).
Japanese Patent Application Publication No. JP02-246075 discloses a configuration in which a file management information block is provided before the BOT of a magnetic tape volume, a file name and location information are written into the file management information block, and the position of the head is determined by referring to the file name and location information when accessing a file.